The examples and perspective in this article deal primarily with the United States and do not represent a worldwide view of the subject.(April 2019) |
Electrical muscle stimulation (EMS), also known as neuromuscular electrical stimulation (NMES) or electromyostimulation, is the elicitation of muscle contraction using electric impulses. EMS has received an increasing amount of attention in the last few years for many reasons: it can be utilized as a strength training tool for healthy subjects and athletes; it could be used as a rehabilitation and preventive tool for people who are partially or totally immobilized; it could be utilized as a testing tool for evaluating the neural and/or muscular function in vivo. EMS has been proven to be more beneficial before exercise and activity due to early muscle activation. Recent studies have found that electrostimulation has been proven to be ineffective during post exercise recovery and can even lead to an increase in Delayed onset muscle soreness (DOMS). [1]
The impulses are generated by the device and are delivered through electrodes on the skin near to the muscles being stimulated. The electrodes are generally pads that adhere to the skin. The impulses mimic the action potential that comes from the central nervous system, causing the muscles to contract. The use of EMS has been cited by sports scientists [2] as a complementary technique for sports training, and published research is available on the results obtained. [3] In the United States, EMS devices are regulated by the U.S. Food and Drug Administration (FDA). [4]
Electrical muscle stimulation can be used as a training, [7] [8] [9] therapeutic, [10] [11] or cosmetic tool.
In medicine, EMS is used for rehabilitation purposes, for instance in physical therapy in the prevention muscle atrophy due to inactivity or neuromuscular imbalance, which can occur for example after musculoskeletal injuries (damage to bones, joints, muscles, ligaments and tendons). This is distinct from transcutaneous electrical nerve stimulation (TENS), in which an electric current is used for pain therapy. "The main difference is the desired outcome. TENS unit is a medical device for pain relief. The desired outcome is to reduce pain by stimulating different nerve signals. EMS fitness is also an FDA-cleared medical device but meant for muscle development. EMS fitness is designed to stimulate all the major muscle groups to elicit strength and endurance adaptations." [12] In the case of TENS, the current is usually sub-threshold, meaning that a muscle contraction is not observed.[ original research? ]
For people who have progressive diseases such as cancer or chronic obstructive pulmonary disease, EMS is used to improve muscle weakness for those unable or unwilling to undertake whole-body exercise. [13] EMS may lead to statistically significant improvement in quadriceps muscle strength, however, further research is needed as this evidence is graded as low certainty. [14] The same study also indicates that EMS may lead to increased muscle mass. [13] Low certainty evidence indicates that adding EMS to an existing exercise programme may help people who are unwell spend fewer days confined to their beds. [15]
During EMS training, a set of complementary muscle groups (e.g., biceps and triceps) are often targeted in alternating fashion, for specific training goals, [16] such as improving the ability to reach for an item.
The FDA rejects certification of devices that claim weight reduction. [17] EMS devices cause a calorie burning that is marginal at best: calories are burnt in significant amount only when most of the body is involved in physical exercise: several muscles, the heart and the respiratory system are all engaged at once. [18] However, some authors imply that EMS can lead to exercise since people toning their muscles with electrical stimulation are more likely afterwards to participate in sporting activities as the body becomes ready, fit, willing and able to take on physical activity. [16]
"Strength training by NMES does promote neural and muscular adaptations that are complementary to the well-known effects of voluntary resistance training". [19] This statement is part of the editorial summary of a 2010 world congress of researchers on the subject. Additional studies on practical applications, which came after that congress, pointed out important factors that make the difference between effective and ineffective EMS. [20] [21] This in retrospect explains why in the past some researchers and practitioners obtained results that others could not reproduce. Also, as published by reputable universities, EMS causes adaptation, i.e. training, of muscle fibers. [22] Because of the characteristics of skeletal muscle fibers, different types of fibers can be activated to differing degrees by different types of EMS, and the modifications induced depend on the pattern of EMS activity. [23] These patterns, referred to as protocols or programs, will cause a different response from contraction of different fiber types. Some programs will improve fatigue resistance, i.e. endurance, others will increase force production. [24]
Luigi Galvani (1761) provided the first scientific evidence that current can activate muscle. During the 19th and 20th centuries, researchers studied and documented the exact electrical properties that generate muscle movement. [25] [26] It was discovered that the body functions induced by electrical stimulation caused long-term changes in the muscles. [27] [28] In the 1960s, Soviet sport scientists applied EMS in the training of elite athletes, claiming 40% force gains. [29] In the 1970s, these studies were shared during conferences with the Western sport establishments. However, results were conflicting, perhaps because the mechanisms in which EMS acted were poorly understood. [30] Medical physiology research [31] [23] pinpointed the mechanisms by which electrical stimulation causes adaptation of cells of muscles, blood vessels [32] [33] [34] and nerves. [24]
The U.S. Food and Drug Administration (FDA) certifies and releases EMS devices into two broad categories: over-the counter devices (OTC), and prescription devices. OTC devices are marketable only for muscle toning; prescription devices can be purchased only with a medical prescription for therapy. Prescription devices should be used under the supervision of an authorized practitioner, for the following uses:
The FDA mandates that manuals prominently display contraindication, warnings, precautions and adverse reactions, including: no use for wearer of pacemaker; no use on vital parts, such as carotid sinus nerves, across the chest, or across the brain; caution in the use during pregnancy, menstruation, and other particular conditions that may be affected by muscle contractions; potential adverse effects include skin irritations and burns
Only FDA-certified devices can be lawfully sold in the US without medical prescription. These can be found at the corresponding FDA webpage for certified devices. [35] The FTC has cracked down on consumer EMS devices that made unsubstantiated claims; [36] many have been removed from the market, some have obtained FDA certification.
Non-professional devices target home-market consumers [37] with wearable units in which EMS circuitry is contained in belt-like garments (ab toning belts) or other clothing items.
The Relax-A-Cizor was one brand of device manufactured by the U.S. company Relaxacizor, Inc. [38] [39] [40] [41] [42] [43]
From the 1950s, the company marketed the device for use in weight loss and fitness. Electrodes from the device were attached to the skin and caused muscle contractions by way of electrical currents. [38] The device caused 40 muscular contractions per minute in the muscles affected by the motor nerve points in the area of each pad. The directions for use recommended use of the device at least 30 minutes daily for each figure placement area, and suggested that the user might use it for longer periods if they wished. The device was offered in a number of different models which were powered either by battery or household current. [44]
Relax-A-Cizors had from 1 to 6 channels. Two pads (or electrodes) were connected by wires to each channel. The user applied from 2 to 12 pads to various parts of their body. For each channel there was a dial which purported to control the intensity of the electrical current flowing into the user's body between the two pads connected to that channel. [44]
As of 1970, the device was manufactured in Chicago, Illinois, by Eastwood Industries, Inc., a wholly owned subsidiary of Relaxacizor, Inc., and was then distributed throughout the country at the direction of Relaxacizor, Inc., or Relaxacizor Sales, Inc. [44]
The device was banned by the United States Food and Drug Administration in 1970 as it was deemed to be potentially unhealthy and dangerous to the users. [38] [44] The case went to court, and the United States District Court for the Central District of California held that the Relax-A-Cizor was a "device" within the meaning of 21 U.S.C. § 321 (h) because it was intended to affect the structure and functions of the body as a girth reducer and exerciser, and upheld the FDA's assertions that the device was potentially hazardous to health. [44]
The FDA informed owners of Relax-A-Cizors that second-hand sale of Relax-A-Cizors was illegal, and recommended that they should destroy the devices or render them inoperable. [42]
Slendertone is another brand name. [45] As of 2015 [update] the company's Slendertone Flex product had been approved by the U.S. Food and Drug Administration for over-the-counter sale for toning, strengthening and firming abdominal muscles. [46]
Lambert–Eaton myasthenic syndrome (LEMS) is a rare autoimmune disorder characterized by muscle weakness of the limbs.
The muscular system is an organ system consisting of skeletal, smooth, and cardiac muscle. It permits movement of the body, maintains posture, and circulates blood throughout the body. The muscular systems in vertebrates are controlled through the nervous system although some muscles can be completely autonomous. Together with the skeletal system in the human, it forms the musculoskeletal system, which is responsible for the movement of the body.
Skeletal muscles are organs of the vertebrate muscular system and typically are attached by tendons to bones of a skeleton. The muscle cells of skeletal muscles are much longer than in the other types of muscle tissue, and are often known as muscle fibers. The muscle tissue of a skeletal muscle is striated – having a striped appearance due to the arrangement of the sarcomeres.
Weakness is a symptom of many different medical conditions. The causes are many and can be divided into conditions that have true or perceived muscle weakness. True muscle weakness is a primary symptom of a variety of skeletal muscle diseases, including muscular dystrophy and inflammatory myopathy. It occurs in neuromuscular junction disorders, such as myasthenia gravis.
A transcutaneous electrical nerve stimulation is a device that produces mild electric current to stimulate the nerves for therapeutic purposes. TENS, by definition, covers the complete range of transcutaneously applied currents used for nerve excitation, but the term is often used with a more restrictive intent—namely, to describe the kind of pulses produced by portable stimulators used to reduce pain. The unit is usually connected to the skin using two or more electrodes which are typically conductive gel pads. A typical battery-operated TENS unit is able to modulate pulse width, frequency, and intensity. Generally, TENS is applied at high frequency (>50 Hz) with an intensity below motor contraction or low frequency (<10 Hz) with an intensity that produces motor contraction. More recently, many TENS units use a mixed frequency mode which alleviates tolerance to repeated use. Intensity of stimulation should be strong but comfortable with greater intensities, regardless of frequency, producing the greatest analgesia. While the use of TENS has proved effective in clinical studies, there is controversy over which conditions the device should be used to treat.
A microcurrent electrical neuromuscular stimulator or MENS is a device used to send weak electrical signals into the body. Such devices apply extremely small microamp [uA] electrical currents to the tissues using electrodes placed on the skin. One microampere [uA] is 1 millionth of an ampere and the uses of MENS are distinct from those of "TENS" which runs at one milliamp [mA] or one thousandth of an amp.
Delayed onset muscle soreness (DOMS) is the pain and stiffness felt in muscles after unaccustomed or strenuous exercise. The soreness is felt most strongly 24 to 72 hours after the exercise. It is thought to be caused by eccentric (lengthening) exercise, which causes small-scale damage (microtrauma) to the muscle fibers. After such exercise, the muscle adapts rapidly to prevent muscle damage, and thereby soreness, if the exercise is repeated.
Muscle fatigue is when muscles that were initially generating a normal amount of force, then experience a declining ability to generate force. It can be a result of vigorous exercise, but abnormal fatigue may be caused by barriers to or interference with the different stages of muscle contraction. There are two main causes of muscle fatigue: the limitations of a nerve’s ability to generate a sustained signal ; and the reduced ability of the muscle fiber to contract.
Functional electrical stimulation (FES) is a technique that uses low-energy electrical pulses to artificially generate body movements in individuals who have been paralyzed due to injury to the central nervous system. More specifically, FES can be used to generate muscle contraction in otherwise paralyzed limbs to produce functions such as grasping, walking, bladder voiding and standing. This technology was originally used to develop neuroprostheses that were implemented to permanently substitute impaired functions in individuals with spinal cord injury (SCI), head injury, stroke and other neurological disorders. In other words, a person would use the device each time he or she wanted to generate a desired function. FES is sometimes also referred to as neuromuscular electrical stimulation (NMES).
Erotic electrostimulation is a sexual practice involving the application of electrical stimulation to the nerves of the body, with particular emphasis on the genitals, using a power source for purposes of sexual stimulation. Electrostimulation has been associated with BDSM activities, and erotic electrostimulation is an evolution of that practice.
Electromyography (EMG) is a technique for evaluating and recording the electrical activity produced by skeletal muscles. EMG is performed using an instrument called an electromyograph to produce a record called an electromyogram. An electromyograph detects the electric potential generated by muscle cells when these cells are electrically or neurologically activated. The signals can be analyzed to detect abnormalities, activation level, or recruitment order, or to analyze the biomechanics of human or animal movement. Needle EMG is an electrodiagnostic medicine technique commonly used by neurologists. Surface EMG is a non-medical procedure used to assess muscle activation by several professionals, including physiotherapists, kinesiologists and biomedical engineers. In computer science, EMG is also used as middleware in gesture recognition towards allowing the input of physical action to a computer as a form of human-computer interaction.
Muscle contraction is the activation of tension-generating sites within muscle cells. In physiology, muscle contraction does not necessarily mean muscle shortening because muscle tension can be produced without changes in muscle length, such as when holding something heavy in the same position. The termination of muscle contraction is followed by muscle relaxation, which is a return of the muscle fibers to their low tension-generating state.
Electrotherapy is the use of electrical energy as a medical treatment. In medicine, the term electrotherapy can apply to a variety of treatments, including the use of electrical devices such as deep brain stimulators for neurological disease. The term has also been applied specifically to the use of electric current to speed wound healing. Additionally, the term "electrotherapy" or "electromagnetic therapy" has also been applied to a range of alternative medical devices and treatments.
Muscle weakness is a lack of muscle strength. Its causes are many and can be divided into conditions that have either true or perceived muscle weakness. True muscle weakness is a primary symptom of a variety of skeletal muscle diseases, including muscular dystrophy and inflammatory myopathy. It occurs in neuromuscular junction disorders, such as myasthenia gravis. Muscle weakness can also be caused by low levels of potassium and other electrolytes within muscle cells. It can be temporary or long-lasting. The term myasthenia is from my- from Greek μυο meaning "muscle" + -asthenia ἀσθένεια meaning "weakness".
Triethylcholine is a drug which mimics choline, and causes failure of cholinergic transmission by interfering with synthesis of acetylcholine in nerve endings.
Eccentric training is a type of strength training that involves using the target muscles to control weight as it moves in a downward motion. This type of training can help build muscle, improve athletic performance, and reduce the risk of injury. An eccentric contraction is the motion of an active muscle while it is lengthening under load. Eccentric training is repetitively doing eccentric muscle contractions. For example, in a biceps curl the action of lowering the dumbbell back down from the lift is the eccentric phase of that exercise – as long as the dumbbell is lowered slowly rather than letting it drop.
Veinoplus is a class IIa medical device with CE marking. It is indicated for the treatment of vascular diseases. This is a neuromuscular stimulator developed by an American scientist, Jozef Cywinski.
Jozef Cywinski is a Polish-American scientist, a specialist in the field of biomedical engineering and specifically in electrical stimulation of living organisms. His work has been the subject of 12 patents, two books and over 100 scientific publications. He developed several first-on-the-market electro-medical devices like cardiac stimulators pacemakers, train-of-four nerve stimulators, PACS, EMS, TENS and Veinoplus calf pump stimulators.
Neuromechanics is an interdisciplinary field that combines biomechanics and neuroscience to understand how the nervous system interacts with the skeletal and muscular systems to enable animals to move. In a motor task, like reaching for an object, neural commands are sent to motor neurons to activate a set of muscles, called muscle synergies. Given which muscles are activated and how they are connected to the skeleton, there will be a corresponding and specific movement of the body. In addition to participating in reflexes, neuromechanical process may also be shaped through motor adaptation and learning.
Blood flow restriction training / Occlusion Training or Occlusion Training or KAATSU is an exercise and rehabilitation modality where resistance exercise, aerobic exercise or physical therapy movements are performed while using an Occlusion Cuff which is applied to the proximal aspect of the muscle on either the arms or legs. In this novel training method developed in Japan by Dr. Yoshiaki Sato in 1966, limb venous blood flow is restricted via the occlusion cuff throughout the contraction cycle and rest period. This result is partial restriction of arterial inflow to muscle, but, most significantly, it restricts venous outflow from the muscle. Given the light-load and strengthening capacity of BFR training, it can provide an effective clinical rehabilitation stimulus without the high levels of joint stress and cardiovascular risk associated with heavy-load training.
Relax-a-cizor.
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